Safety blasting composition with a metal formate as a fuel



United States. Patent 3,356,546 SAFETY BLASTING COMPOSITION WITH A METAL FORMATE AS A FUEL William Dick, Stevenston, and Owen Allen G urton, Fairlie, Ayrshire, Scotland, assignors to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Nov. 14, 1966, Ser. No. 593,721 Claims priority, application Great Britain,

Dec. 1, 1965, 50,982/65 5 Claims. (Cl. 149-47) ABSTRACT OF THE DISCLOSURE Safety blasting explosives which do not burn under atmospheric pressure and which have lessened tendency to ignite fire-damp. The explosives contain, by we ght, 12-25% self-explosive sensitising agent such as mt roglycerine, nitroglycol or nitrotoluene, 25-50% oxidising salt such as metal nitrates and ammonium nitrate, -30% flame quenching salt such as metal chlorides and ammonium chloride and 440% metal formate as fuel, the latter being free from fibrous cellulosic material.

This invention is a modification of the invention described in British specification No. 1,016,462 and relates to improved safety blasting explosive compositions for use in gassy mines.

In British specification No. 1,016,462 safety explosives were described and claimed which comprised 7 to 12% by weight of self-explosive sensitising ingredient, fuel material, oxidising salt and flame quenching salt in such concentrations that the composition had a power (by weight) of 30 to 45% Blasting Gelatine, the fuel material comprising metal formate and being free from fibrous cellulosic material. These explosives, in addition to being very safe for use in coal mines where a danger of the ignition of fire-damp existed, had the further advantage that they could not be caused to burn in a borehole by the detonation of an adjacent cartridge.

The very high degree of safety in fire-damp which these explosives afforded in only necessary in mining conditions where there is a danger of gas filled breaks crossing or being formed across the shotholes. In other conditions such as blasting in solid coal it is possible to use explosives of -a higher power, higher velocity of detonation and containing higher proportions of selfexplosive sensitising material.

Hitherto these more sensitive safety explosives have usually contained fibrous cellulosic material as fuel and were inflammable under atmospheric pressure. We have now found that by eliminating the fibrous cellulosic material and incorporating, as a fuel component, a metal formate, safety explosives may be prepared which will not burn under atmospheric pressure, and which contain up to 25% of self-explosive sensitising ingredient and have powers of up to 50% Blasting Gelatine. These explosives also have less tendency to ignite fire-damp than corresponding explosives containing fibrous cellulosic fuel. Thus a safety blasting explosive composition of this invention comprises 12 and 25% by Weight of self-explosive sensitising ingredient, oxidising salt and flame quenching salt in such concentrations that the composition has a power (by weight) of 30 to 50% Blasting Gelatine, the fuel material comprising metal formate and being free from fibrous cellulosic material. The power decreases with increasing concentrations of flame quenching salt and increases with increasing concentration of the reacting ingredients. The available oxygen of the oxidising salt may be substantially balanced by the formate. The salfexplosive sensitising ingredient may, for example, comprise liquid nitric ester such as, for example, nitroglycerine or nitroglycol which may conveniently be gelatinised with a proportion of nitrocellulose. It may also comprise nitrated hydrocarbons such as nitrotoluene. The metal formate may conveniently constitute 4 to 40% by weight of the composition and may constitute substantially all the fuel present in the composition. Metal formates which may conveniently be used include sodium, potassium, calicum, magnesium, barium and lead formates, and of these we prefer calcium formate because of its ready availability, low solubility and its nou-hydroscopic and non-toxic character. In explosives comprising sodium or ammonium chloride as flame quenching salts and ammonium nitrate as an oxidising salt the preferred composition comprises (by weight) 13 to 20% of liquid nitric ester, 30 to 50% ammonium nitrate, 10 to 30% sodium or ammonium chloride and 20 to 30% of metal formate.

In explosives of the so-called exchanged-ion kind in which sodium nitrate constitutes at least a proportion of the oxidising ingredient and at least a proportion of flame quenching ions is provided by ammonium chloride, the preferred composition comprises (by weight) 13 to 20% liquid nitric ester, 8 to 20% ammonium nitrate, 20 to 30% ammonium chloride, 25 to 40% sodium nitrate and 5 to 20% metal formate.

The invention is further illustrated by the following examples in which all parts and percentages are by weight.

Examples Details and properties of examples in accordance with the invention are included in the following table:

Example n Burning Test Fails to burn.

The explosive compositions of the examples were prepared in a conventional manner and the power and velocity were determined by known methods. In the propagation test the maximum distance for end to end propagation of detonation across an air gap from an initiated cartridge to a receptor cartridge was determined.

In the burning tests a 1%," dia. cartridge was placed upright on the ground and 10 grams of a defiagrating composition were poured into the opened end of the cartridge and ignited -by a fuse. The defiagrating composition consisted of 30% black copper oxide, 60% calcium silicide, 10% red ochre.

When this test fas carried out on a conventional explosive containing a fibrous cellulosic fuel, the explosive was invariably ignited by the defiagrating composition and continued to burn or smoulder. None of the compositions of examples continued to burn after the deflagrating composition was exhausted.

What we claim is:

1. A safety blasting explosive for gassy mines comprising 12 to 25 by weight of an explosive sensitiser selected from the group consisting of self-explosive liquid nitric esters of polyhydric alcohols, trinitrotoluene and nitrocellulose, 25 to 50% by weight of an oxidising salt selected from the group consisting of alkali metal nitrates and ammonium nitrate, to 30% by weight of a compound selected from the group consisting of metal chloride and ammonium chloride, and, as fuel, 4 to 40% by weight of metal formate, the explosive composition being free from fibrous cellulosic material.

2. A safety blasting explosive as in claim 1 wherein said explosive sensitiser is selected from the group consisting of nitroglycerine, nitroglycol and trinitrotoluene.

3. A safety blasting explosive composition as claimed in claim 1 wherein the metal formate is selected from the group consisting of sodium, potassium, calcium, magnesium, barium and lead formates.

4. A safety blasting explosive composition as claimed in claim 1 comprising (by weight) 13 to 20% liquid nitric ester, 30 to 50% of ammonium nitrate, 10 to 30% of a compound selected from the group consisting of sodium chloride and ammonium chloride and 20 to 30% of metal formate.

5. A safety blasting explosive composition as claimed in 4- claim 1 comprising (by weight) 13 to 20% liquid nitric ester, 8 to 20% ammonium nitrate, 20 to ammonium chloride, 25 to sodium nitrate and 5 to 20% metal formate.

References Cited UNITED STATES PATENTS CARL D. QUARFORTH, Primary Examiner. BENJAMIN R. PADGE'IT, Examiner. S. I. LECHERT, JR., Assistant Examiner. 

1. A SAFETY BLASTING EXPLOSIVE FOR GASSY MINES COMPRISING 12 TO 25% BY WEIGHT OF AN EXPLOSIVE SENSITISER SELECTED FROM THE GROUP CONSISTING OF SELF-EXPLOSIVE LIQUID NITRIC ESTERS OF POLYDYDRIC ALCOHOLS, TRINITROTOLUENE AND NITROCELLULOSE, 25 TO 50% BY WEIGHT OF AN OXIDISING SALT SELECTED FROM THE GROUP CONSISTING OF ALKAKI METAL NITRATES AND AMMONIUM NITRATE, 10 TO 30% BY WEIGHT OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF METAL CHLORIDE AND AMMONIUM CHLORIDE, AND, AS FUEL, 4 TO 40% BY WEIGHT OF METAL FORMATE, THE EXPLOSIVE COMPOSITION BEING FREE FROM FIBROUS CELLULOSIC MATERIAL. 